Sneutrino Dark Matter In Supersymmetry Models And Interpretations Of DAMPE Excess

Though a large number of experimental results coincide with the theoretical predictions of the standard model?SM?,some of the defects of the SM still hint the existences of new physics.For example,SM can not provide dark matter candidates and explain the neutrino mass.As a popular ultraviolet-complete Beyond Standard Model?BSM?,Supersymmetric model?SUSY?can naturally provide dark matter candidates,but still can not explain the mass of neutrinos.Seesaw mechanism as a way to generate neutrino mass,combined with supersymmetric model can solve the dark matter problem and the neutrino puzzle at the same time.Recently,we have completed following work in this direction:·In the Next-to-Minimal Supersymmetric Standard Model?NMSSM?with Type-I seesaw mechanism,we study the scenario of sneutrino as a dark matter candidate.We first give the analytical formulas of dark matter observables,analyze the different annihilation mech-anisms of dark matter,and define a physical quantity to parameterize the fine tuning of direct detection.Then we construct likelihood function with B-physics measurements,L-HC Higgs data,DM relic density and its direct and indirect search limits,and perform a comprehensive scan over the parameter space of the theory by Nested Sampling method.We adopt both bayesian and frequentist statistical quantities to illustrate the favored pa-rameter space of the scenarios,the DM annihilation mechanism as well as the features of DM-nucleon scattering.We find that the scenarios are viable over broad parameter regions,and the DM usually co-annihilated with the Higgsinos to get the measured relic density.Interestingly,our results indicate that a rather low Higgsino mass,?250GeV,is preferred in the scan,and the DM-nucleon scattering rate is naturally suppressed to coincide with the recent XENON-1T results.Other issues,such as the LHC search for the Higgsinos,are also addressed.·In the Next-to-Minimal Supersymmetric Standard Model?NMSSM?with inverse seesaw mechanism,we study the scenario of sneutrino as dark matter under the requirement of naturalness.First,we extend the NMSSM by inverse seesaw mechanism to generate neutrino mass.Then,we construct the likelihood function by considering the experimental data of Higgs,B physics and dark matter,and scan the parameter space by MCMC?Markov Chain Monte Carlo?sampling method.Our results show that in certain parameter space the lightest sneutrino may act as a viable DM candidate,i.e.it can annihilate by multi-channels to get correct relic density and meanwhile satisfy all experimental constraints.The most striking feature of the extension is that the DM-nucleon scattering rate can be naturally below its current experimental bounds regardless of the higgsino mass,and hence it alleviates the tension between naturalness and DM experiments.Other interesting features include that the Higgs phenomenology becomes much richer than that of the original NMSSM due to the relaxed constraints from DM physics and also due to the presence of extra neutrinos.In addition,with the DArk Matter Particle Explorer?DAMPE?experiment released the new measurement of the total cosmic e⁺+e^-flux between 25 GeV and 4.6 TeV and reported a hint of an excess in the e⁺e^-spectrum at around 1.4 TeV,the interpretations of this excess has become a hot point.We have completed the following work in this direction:·We utilize the scalar dark matter?DM?annihilation scenario to explain the DAMPE peak by extending G_SM?SU?3?_C×SU?2?_L×U?1?_Ywith additional U?1?gauge symmetries while keeping anomaly free to generate???Z^?Z^??????^??^?,where?,Z^?,?^???denote the scalar DM,the new gauge boson and?^???=e,?,?,respectively,with m_??m_Z??2×1.5?TeV?.We first illustrate that the minimal framework G_SM×U?1?_Y?with the above mass choices can explain the DAMPE excess but has been excluded by LHC constraints from the Z^?searches.Then we study a non-minimal framework G_SM×U?1?_Y?×U?1?_Y??in which U?1?_Y??mixes with U?1?_Y?.We show that such a framework can interpret the DAMPE data while passing other constraints including the DM relic abundance,DM direct detection and collider bounds.We also investigate the predicted e⁺e^-spectrum in this framework and find that the mass splitting?m=m_?-m_Z?should be less than about 17 GeV to produce the peak-like structure.·In this work we utilize the minimal LRSM to study the recently reported DAMPE results of cosmic e⁺e^-spectrum which exhibits a tentative peak around 1.4 TeV,while satisfying the current neutrino data.We propose to explain the DAMPE peak with a complex scalar DM?in two scenarios:1)??^*?H₁⁺⁺H₁^--??_i⁺?_i⁺?_j^-?_j^-;2)??^*?H_k⁺⁺H_k^--??_i⁺?_i⁺?_j^-?_j^-accompanied by??^*?H₁⁺H₁^-??_i⁺?_?i?_j^-?_?jwith?_i,j=e,?,?and k=1,2.We fit the theoretical prediction on e⁺e^-spectrum to relevant experimental data to determine the scalar mass spectrum favored by the DAMPE excess.We also consider various constraints from theoretical principles,collider experiments as well as DM relic density and direct search experiments.We find that there are ample parameter space which can interpret the DAMPE data while passing the constraints.Our explanations,on the other hand,usually imply the existence of other new physics at the energy scale ranging from 10⁷GeV to 10¹¹GeV.Collider tests of our explanations are also discussed.·Inspired by the peak structure observed by recent DAMPE experiment in e⁺e^-cosmic-ray spectrum,we consider a scalar dark matter?DM?model with gauged U?1?_Le-L?symmetry,which is the most economical anomaly-free theory to potentially explain the peak by DM annihilation in nearby subhalo.We utilize the process???Z^?Z^??l?ll^??l^?,where?,Z^?,l^???denote the scalar DM,the new gauge boson and l^???=e,?,respectively,to generate the e⁺e^-spectrum.By fitting the predicted spectrum to the experimental data,we obtain the favored DM mass range m_??3060⁺⁸⁰_-100GeV and?m?m_?-m_Z?14 GeV at68%Confidence Level?C.L.?.Furthermore,we determine the parameter space of the model which can explain the peak and meanwhile satisfy the constraints from DM relic abundance,DM direct detection and the collider bounds.We conclude that the model we consider can account for the peak,although there exists a tension with the constraints from the LEP-II bound on m_Z?arising from the cross section measurement of e⁺e^-?Z^?*?e⁺e^-.In conclusion,our research on sneutrino dark matter can provide some clues for the direct detection of dark matter and the discovery of new physics in collider experiments.And our work on DAMPE excess provide meaningful explanations for the indirect detection of dark matter.